Red yeast rice contains a compound called monacolin K (also known as lovastatin) that reduces production of cholesterol by inhibiting HMG-CoA reductase, a key enzyme in cholesterol synthesis.⁵ Multiple clinical trials have shown red yeast rice can effectively lower high total, LDL-, and non-HDL-cholesterol levels. In fact, six to eight weeks of treatment with red yeast rice extract has been found to reduce LDL-cholesterol levels by 15–25%.⁶

Lovastatin (Mevacor)and several of its analogs, collectively called statins, are used as prescription drugs used to treat high cholesterol.⁵ However, a typical daily dose of red yeast rice extract provides 10 mg or less monacolin K, while a common dose of lovastatin is 20 to 40 mg per day.⁶ It has been suggested that other compounds, including other monacolins, present in red yeast rice work together with monacolin K to produce a greater cholesterol-lowering effect than would be expected from the small amount of monacolin K alone.⁵ Nevertheless, monacolins in red yeast rice products vary widely and are often not accurately quantified on labels, and red yeast rice has demonstrated a similar adverse side effect profile to lovastatin.^10,11 Because HMG-CoA reductase also plays a role in synthesis of coenzyme Q10, an antioxidant needed for mitochondrial energy production, a small amount of coenzyme Q10 is sometimes included in red yeast rice supplements.¹²

A randomized controlled trial comparing a monacolin K-containing red yeast rice product and a monacolin K-free red yeast rice product to placebo found only the monacolin K-containing supplement lowered cholesterol levels.¹³ An uncontrolled clinical trial in 25 subjects with low to moderate cardiovascular risk found supplementing with red yeast rice providing 3 mg monacolin K plus 30 mg of coenzyme Q10 daily for one year reduced total, LDL-, and non-HDL-cholesterol, as well as triglyceride and high-sensitivity C-reactive protein (hs-CRP, a marker of vascular inflammation) levels. In addition, vascular characteristics had improved at the end of the trial.¹⁴ In a controlled trial that included 104 participants with high cholesterol levels enrolled in a diet and lifestyle program, those additionally treated with a red yeast rice supplement providing 10 mg monacolin K and 30 mg coenzyme Q10 per day had greater reductions in total and LDL-cholesterol levels, as well as blood pressure, than those receiving no supplements.¹⁵

Although primarily used to lower high serum cholesterol, red yeast rice extract, high in monacolins, has been found to significantly lower serum triglyceride levels.¹³ People in the trial took 1.2 grams (approximately 13.5 mg total monacolins) of a concentrated red yeast rice extract per day for two months. The sale of Cholestin has been banned in the United States, as a result of a lawsuit alleging patent infringement. Other red yeast rice products currently on the market differ from Cholestin in their chemical makeup. None contain the full complement of 10 monacolin compounds that are present in Cholestin, and some contain a potentially toxic fermentation product called citrinin. ¹⁴ Until further information is available, red yeast rice products other than Cholestin cannot be recommended.